It is our contention that gangland residence may have a unique effect on population health that is not reducible to crime, even if we were able to objectively and accurately measure crime. The nature of gang activities and violence remains a plausibly unique contributor to population health-a factor that has been largely unexplored despite its potential effect on population health and health disparities. We further argue that birh outcomes are a relevant barometer for population health, given the responsiveness of this outcome to changing social conditions and due to the fact that we are able to assess birth outcomes with a large sample in highly diverse neighborhood settings, over a long period of time. Our project goals for this exploratory/developmental (R21) research proposal are simple, we want to assess whether gangland residence is associated with population health and health disparities. Given the pervasiveness of gangs in Los Angeles County, the large variation in neighborhood types, and the responsiveness of birth outcomes to dynamic social conditions-this project has the capability to shed light on an under-researched social determinant of health. Our aims are as follows: Aim 1. To determine if gangland residence has an independent effect on adverse birth outcomes, net of neighborhood crime and socio-demographics such as poverty and economic and racial/ethnic composition. Aim 2. To determine if gangland residence compounds the effect of neighborhood-level crime. Aim 3. To determine whether gang injunctions are efficacious for improving population health. Aim 4. To assess whether gangland residence accounts for adverse birth outcome disparities. This project is an attempt to uncover independent effects of gangland residence on population health and if successful, will provide a baseline for future gangland community health research. We believe the project's innovation will assuage any fears of it being a relatively risky endeavor and that is why we feel that an R21 is the perfect mechanism for such an approach.